Biomedical subjects
Publications and source records attributed to K Oritani.
Many aspects of blood cell formation can now be modeled in culture and rapid progress is being made in understanding how blood cell precursors interact with unique components of their environment. This brief review considers some cell interaction molecules that may be important for controlling the position of cells within, as well as their egress from, bone marrow.
Beta1-4 N-acetylglucosaminyltransferase III (GnT-III) synthesizes bisecting N-acetylglucosamine structures on asparagine-linked oligosaccharides. Using B16-hm mouse melanoma cells stably expressing GnT-III activity as positive transfectants, the effect of bisecting N-acetylglucosamine on the function of CD44 was analyzed in association with adhesion to hyaluronate and tumor spread in mice. Transfection of GnT-III caused increased affinity of immunoprecipitated CD44 to erythro-agglutinating phytohemagglutinin, that preferentially recognizes bisecting N-acetylglucosamine, without affecting the surface CD44 amount, indicating an increase in bisecting N-acetylglucosamine residues on CD44 in positive transfectants. CD44-mediated adhesion to immobilized hyaluronate and the binding of fluorescence-labeled hyaluronate to the cell surface were increased in positive transfectants. The enhanced adhesion in positive transfectants was suppressed by the treatment with beta-N-acetylhexosaminidase, indicating that N-acetylglucosamine residues were responsible for the enhanced adhesion. Positive transfectants showed promoted CD44-mediated tumor growth and metastatic development in the spleen after subcutaneous inoculation into mice. These results indicate that glycosylation of CD44 due to GnT-III causes enhanced adhesion to hyaluronate, local tumor growth and metastatic growth in spleen, suggesting that the CD44-mediated adhesion and tumor spread can be modified through introduction of a glycosyltransferase gene.
The extracellular matrix produced by stromal cells plays a critical role in lympho-hematopoiesis. It was recently discovered that matrix glycoprotein SC1/ECM2 is a component of that matrix and preliminary evidence suggested that it could contribute to the nurturing environment for B-lymphocyte precursors. A fusion protein prepared from the amino terminal portion of SC1/ECM2 and the constant region of human Ig preferentially bound to pre-B cells. Furthermore, the cloning efficiency of interleukin-7-dependent B-cell precursors was increased in a dose-dependent manner by addition of this fusion protein. We now report the complete cDNA sequence for murine SC1/ECM2 and its localization to the central region of chromosome 5. A fusion protein prepared from the full length of SC1/ECM2 and Ig was found to recognize pre-B cells in a divalent cation-dependent manner, and to augment mitogen-dependent proliferation of mature B cells, as well as the cloning of pre-B cells, but to have no influence on myeloid progenitor cells. Although SC1/ECM2 is normally a secreted protein, we show that it is also capable of augmenting lymphopoiesis when expressed as a transmembrane protein on fibroblasts. Although the C-terminal portion of SC1/ECM2 has sequence homology to osteonectin/SPARC, the unique N-terminal one fifth of the protein was sufficient to augment lymphocyte growth.
Although thrombopoietin (TPO) is known to play a fundamental role in both megakaryopoiesis and thrombopoiesis, the molecular mechanism of TPO-induced megakaryocytic differentiation is not known. In a human megakaryoblastic leukemia cell line, CMK, that showed some degree of megakaryocytic differentiation after culture with TPO, the cyclin-dependent kinase (Cdk) inhibitor p21(WAF1/Cip1), but not p27(Kip1), p16(INK4A), p15(INK4B), or p18(INK4C), was found to be upregulated in an immediately early response to TPO. The expression of p21 was found to be sustained over a period of 5 days by treatment with TPO in large polyploid cells that developed in response to TPO, but not in small undifferentiated cells, indicating a close correlation between the ligand-induced differentiation and p21 induction in CMK cells. To examine potential roles of Cdk inhibitors in megakaryocytic differentiation, CMK cells were transfected with the p21, p27, or p16 gene, together with a marker gene, beta-galactosidase, and were cultured with medium alone for 5 days. The ectopic expression of p21 or p27 but not of p16 led to induction of megakaryocytic differentiation of CMK cells. Overexpression of the N-terminal domain (amino acids [aa] 1 to 75) of p21 was sufficient to induce megakaryocytic differentiation, whereas that of the C-terminal domain (aa 76 to 164) had little or no effect on morphological features. Furthermore, we found that although TPO induced tyrosine phosphorylation of both STAT3 and STAT5 in CMK cells, only STAT5 showed binding activities to potential STAT-binding sites that locate in the promoter region of p21 gene (p21-SIE sites), thereby leading to transactivation of p21. These results suggested that p21 induction, possibly mediated through activated STAT5, could play an important role in TPO-induced megakaryocytic differentiation.
The c-kit proto-oncogene encodes a receptor tyrosine kinase that is crucial to hematopoiesis, melanogenesis, and gametogeneis. Although the enzymatic activity of the c-kit product (KIT) is regulated by its ligand, both the Val559-->Gly (G559) mutation in the juxtamembrane domain and the Asp814-->Val (V814) mutation in the phosphotransferase domain lead to constitutive activation of KIT. By retroviral infection of hematopoietic progenitor cells with KIT(G559) or KIT(V814), KIT(G559) induced development of granulocyte/macrophage and mast-cell colonies in vitro without the addition of exogenous growth factors. KIT(V814) induced factor-independent growth of various types of hematopoietic progenitor cells, resulting in the development of mixed erythroid/myeloid colonies in addition to granulocyte/macrophage and mast-cell colonies. Furthermore, transplantation of KIT(G559) and KIT(V814)-infected bone marrow cells led to development of acute leukemia in one of 10 and six of 10 transplanted mice, respectively. No mice developed hematologic malignancies after transplantation of wild-type KIT-infected cells. Furthermore, transgenic mice expressing KIT(V814) developed acute leukemia or malignant lymphoma. These results demonstrate a direct role of the mutant KITs, particularly KIT(V814), in tumorigenesis of hematopoietic cells and suggest that similar mutations may contribute to the development of human hematologic malignancies.
We recently described an mAb (MTS23) reactive with a membrane Ag expressed on a subset of thymic medullary stromal cells. This Ag is also constitutively expressed at high levels on peripheral B cells, macrophages, and thymic and splenic dendritic cells of C57BL/6 mice. A number of stromal cell lines derived from thymus and bone marrow also stain with MTS23, but thymocytes and peripheral T cells only weakly express the Ag detected by MTS23. Here we show that the molecule detected by MTS23 is a member of the Ly-6 family of phosphatidylinositol-anchored membrane proteins. Treatment of stromal cells with phosphatidylinositol-phospholipase C before staining completely abolished expression. Using transient expression of 293T cells and a cDNA library of a stromal cell line cloned into the pEF-BOS vector, a cDNA encoding the MTS23-target Ag was isolated. Partial sequencing and restriction enzyme mapping revealed that it represents the Ly-6A/E protein. While the physiologic significance of the presence of Ly-6 molecules on stromal cells is not clear, it has been known for some time that, at least in lymphocytes, cellular activation events can be induced upon Ly-6 engagement. We now demonstrate that Ly-6 also functions as a signal transduction molecule on stromal cells, in that granulocyte-macrophage CSF can be produced by a variety of stromal cell lines upon mAb-mediated cross-linking of Ly-6. Together with the dramatic up-regulation of Ly-6 expression on stromal cells upon IFN-gamma treatment, this is the first indication of a biologic function of an Ly-6 gene product on nonhemopoietic cells. The results suggest that Ly-6 may play a role in the cross-talk between lymphocyte precursors and stromal cells.
The KMC8.8 monoclonal antibody was made by immunizing rats with the BMS2 stromal cell clone, and was selected for further study because its ability to inhibit production of myeloid cells in Dexter cultures but not that of lymphoid cells in Whitlock-Witte cultures. The influence on myeloid progenitors might have been indirect, since the antibody did not prevent responsiveness to colony-stimulating factors in semisolid agar cultures. Furthermore, there was no inhibition, and some augmentation, of cell production when the antibody was added to established Dexter cultures. A cDNA clone that encoded the KMC8.8-recognized molecule was isolated by expression cloning and found to be identical in sequence to a previously published murine CD9 homologue. The antibody and cDNA clone were used to establish that CD9 is expressed by stromal cells, megakaryocytes, platelets, myeloid cells, and subpopulations of mature lymphocytes in mice. Treatment with the KMC8.8/CD9 antibody slightly augmented adhesion between myeloid cells and stromal cells, consistent with previous reports that this member of the tetraspan family of proteins can transmit proadhesive signals to human platelets and lymphoid cells. CD9 might participate in cell-cell interactions critical for correct orientation and movement of maturing myeloid cells in bone marrow.
Our understanding of lympho-hematopoietic microenvironments is incomplete, and a new cloning strategy was developed to identify molecules that bind to B lineage lymphocyte precursors. A cell sorting procedure was used for initial enrichment of cDNAs from stromal cell mRNA that contained signal sequences and were therefore likely to encode transmembrane or secreted proteins. A second step involved expression of the library as soluble Ig fusion proteins. Finally, pools representing these proteins were screened for the ability to recognize pre-B cells. This approach resulted in the cloning of biglycan, syndecan 4, collagen type I, clusterin, matrix glycoprotein sc1, osteonectin, and one unknown molecule (designated SIM). The full-length cDNA of SIM revealed that it is a type I transmembrane protein, and its intracellular domain has weak homology with myosin heavy chain and related proteins. Staining of established cell lines and freshly isolated hematopoietic cells with the Ig fusion proteins revealed distinct patterns of reactivity and differential dependence on divalent cations. Biglycan-, sc1-, and SIM-Ig fusion proteins selectively increased interleukin 7-dependent proliferation of pre-B cells. Overexpression of the entire SIM protein affected the morphology of 293T cells, while expression of just the extracellular portion was without effect. Thus, a series of stromal cell surface molecules has been identified that interact with blood cell precursors. Three of them promoted the survival and/or proliferation of pre-B cells in culture, and all merit further study in relation to lympho-hematopoiesis.
Although CD44 is expressed on a wide variety of cell types, few of them use it to recognize the ligand hyaluronan (HA). A glycosylation-defective clone of Chinese hamster ovary cells (Lec 8) bound HA, demonstrating that complete processing of glycoproteins with addition of a full complement of sialic acid is not required. On the contrary, subsequent findings revealed that complex sugars on CD44 can actually inhibit ligand recognition. Two subclones of wild-type Chinese hamster ovary cells with similar amounts of surface CD44 were isolated on the basis of HA binding and found to differ with respect to CD44 size as well as staining with fluorescent lectins. Treatment of the nonbinding clone with tunicamycin reduced the size of the protein and allowed the cells to recognize HA via CD44. This function was also induced by treatment with deglycosylating enzymes (either a mixture of endoglycosidase F and N-glycosidase F or neuraminidase alone). A possible role for glycosylation in regulation of adhesion was then sought with a series of normal and transformed murine cells. Disruption of glycosylation or treatment with deglycosylating enzymes did not induce ligand binding in an interleukin 7-dependent pre-B cell line, and splenic B cells also appeared to be in an inactive state. Some normal B cells acquired the ability to recognize HA after stimulation with lipopolysaccharide or interleukin 5 and had distinctive surface characteristics (loss of immunoglobulin D and acquisition of CD43). An additional subset of activated cells might have been in a transitional state, because the cells bound ligand after neuraminidase treatment. The ligand-binding ability of a purified CD44-immunoglobulin fusion protein dramatically increased after neuraminidase treatment. Thus, differential glycosylation of this molecule is sufficient to influence its recognition function. Cell adhesion involving HA can be regulated by multiple mechanisms, one of which involves variable glycosylation of CD44.
Bone marrow stromal cells regulate B-cell growth and development through their surface molecules and cytokines. In this study, we generated a mAb, RS38, that recognized a novel human membrane protein, BST-2, expressed on bone marrow stromal cell lines and synovial cell lines. We cloned a cDNA encoding BST-2 from a rheumatoid arthritis-derived synovial cell line. BST-2 is a 30- to 36-kDa type II transmembrane protein, consisting of 180 amino acids. The BST-2 gene (HGMW-approved symbol BST2) is located on chromosome 19p13.2. BST-2 is expressed not only on certain bone marrow stromal cell lines but also on various normal tissues, although its expression pattern is different from that of another bone marrow stromal cell surface molecule, BST-1. BST-2 surface expression on fibroblast cell lines facilitated the stromal cell-dependent growth of a murine bone marrow-derived pre-B-cell line, DW34. The results suggest that BST-2 may be involved in pre-B-cell growth.
The c-kit receptor tyrosine kinase (KIT) is activated upon ligand binding, thereby leading to a variety of signaling events that play a fundamental role in hematopoiesis. In addition to ligand-dependent activation, we have previously shown that KIT is constitutively activated in a ligand-independent manner by two point mutations, Val-559-->Gly (G559) mutation in the juxtamembrane domain and Asp-814-->Val (V814) mutation in the phosphotransferase domain. To investigate the biochemical consequence and biologic significance of these mutations, retroviral vectors encoding KITG559 or KITV814 were introduced into murine pro-B-type Ba/F3 cells and myeloid FDC-P1 cells, both of which require interleukin-3 (IL-3) for their growth and survival. In the cells, KITG559 or KITV814 were found to be constitutively phophorylated on tyrosine in the absence of stem cell factor (SCF) that is a ligand for KIT. Chemical cross-linking analysis showed that a substantial fraction of the phosphorylated KITG559 underwent dimerization even in the absence of SCF, whereas the phosphorylated KITV814 did not, suggesting the distinct mechanisms underlying constitutive activation of KIT by G559 and V814 mutations. Furthermore, the cells expressing either KITG559 or KITV814 were found to show a factor-independent growth, whereas the cells expressing wild-type KIT (KITWT) proliferated in response to SCF as well as IL-3. Moreover, subcutaneous injection of Ba/F3 cells expressing KITG559 or KITV814 into nude mice resulted in production of large tumors at all sites of the injection within 2 weeks, and all nude mice quickly succumbed to leukemia and died. These results suggest that, although the mechanisms underlying constitutive activation of KITG559 or KITV814 may be different, both of the activating mutations have a function to induce a factor-independent and tumorigenic phenotype. Also, the data of this study raise the possibility that the constitutively activating mutations of c-kit may play a causal role in development of hematologic malignancies.
Antibodies to CD44 have been used to inhibit a variety of processes which include lymphohemopoiesis, lymphocyte migration, and tumor metastasis. Some, but not all, CD44-mediated functions derive from its ability to serve as a receptor for hyaluronan (HA). However, sites on CD44 that interact with either ligands or antibodies are poorly understood. Interspecies rat/mouse CD44 chimeras were used to analyze the specificity of 25 mAbs and to determine that they recognize at least seven epitopes. Amino acid substitutions that resulted in loss of antibody recognition were all located in the region of homology to other cartilage link family proteins. While at least five epitopes were eliminated by single amino acid replacements, multiple residues had to be changed to destroy binding by other antibodies. One antibody was sensitive to changes in any of three separate parts of the molecule and some antibodies to distinct epitopes cross-blocked each other. Certain antibodies had the ability to increase HA binding by lymphocytes but this did not correlate absolutely with antibody specificity and was only partially attributable to CD44 cross-linking. Antibodies that consistently blocked HA recognition were all sensitive to amino acid changes within a short stretch of CD44. Such blocking antibodies interacted with CD44 more strongly than ligand in competition experiments. One large group of antibodies blocked ligand binding, but only with a particular cell line. This detailed analysis adds to our understanding of functional domains within CD44 and requirements for antibodies to influence recognition of one ligand.
Bone marrow stromal cells are essential for B-lymphocyte development. However, how stromal cells regulate B lymphopoiesis is not clear. In this paper, we report the molecular cloning of a stromal cell line-derived glycosyl-phosphatidylinositol-anchored molecule, BST-1, that facilitates pre-B-cell growth. The deduced amino acid sequence of BST-1 exhibited 33% identity with CD38. BST-1 was expressed in a wide range of tissues and in umbilical vein endothelial cells, whereas it was scarcely expressed in a variety of hematopoietic cell lines. The gene for BST-1 was assigned to chromosome 14q32.3, where immunoglobulin heavy-chain genes are clustered. BST-1 expression was enhanced in rheumatoid arthritis patient-derived bone marrow stromal cell lines that were previously shown to have an enhanced ability to support the growth of a pre-B-cell line as compared with stromal cell lines derived from healthy donors.
Extracellular matrix (ECM) molecules such as fibronectin (FN), collagens, and laminin have important roles in hematopoiesis. However, little is known about the precise mechanisms by which ECM molecules regulate proliferation of human hematopoietic progenitor cells. In this study, we have investigated the effects of ECM molecules, particularly of FN, on the proliferation of a myeloid leukemia cell line, M07E, which proliferates in response to either human granulocyte/macrophage colony-stimulating factor (GM-CSF) or stem cell factor (SCF). The [3H]thymidine incorporation and cell enumeration assays showed that FN strikingly inhibited GM-CSF- or SCF-induced proliferation of M07E cells in a dose-dependent manner, whereas little or no inhibition was induced by collagen types I and IV. The growth suppression of M07E cells was not due to the inhibitory effect of FN on ligand binding or very early events in the signal transduction pathways from the GM-CSF or SCF receptors. DNA content analysis using flow cytometry after staining with propidium iodide revealed that the treatment of M07E cells with FN did not block the entry of the cells into the cell cycle after stimulation with GM-CSF or SCF, whereas the treatment resulted in the appearance of subdiploid peak. Furthermore, FN was found to induce oligonucleosomal DNA fragmentation and chromatin condensation in the cells even in the presence of GM-CSF or SCF, suggesting the involvement of programmed cell death (apoptosis) in the FN-induced growth suppression. The growth suppression or apoptosis induced by FN was rescued by the addition of either anti-FN antibody, anti-very late antigen 5 monoclonal antibody (anti-VLA5 mAb), or GRGDSP peptide, but not by that of anti-VLA4 mAb or GRGESP peptide, suggesting that the FN effects on M07E cells were mediated through VLA5. In addition, the FN-induced apoptosis was detectable in VLA5-positive human hematopoietic cell lines other than M07E cells, but not in any of the VLA5-negative cell lines. These results suggest that FN is capable of inducing apoptosis via its interaction with VLA5, and also raise the possibility that the FN-VLA5 interaction may contribute, at least in part, to negative regulation of hematopoiesis.
In order to elucidate the pathologic significance of the bone marrow (BM) microenvironment in multiple myeloma (MM) and rheumatoid arthritis (RA), we established patient- or healthy donor (HD)-derived BM stromal cell lines by transfecting the plasmid for expression of SV40 large T Ag and examined their ability to support the stromal cell-dependent growth of a pre-B cell line, DW34. The means of recovered cell numbers of DW34 co-cultured with MM- and RA-derived BM stromal cell lines ranged from 6- to 10-fold more than those with HD-derived ones. Their enhanced ability to support DW34 cell growth was not caused by cytokines, including IL-6, IL-7, and c-kit ligand, although exogenous IL-7 could augment the growth-supporting ability. DW34 cell growth on the stromal cell lines was abolished by inhibiting cell-to-cell interaction with a membrane filter. FACS analysis revealed that the stromal cell lines did not express LFA-1 alpha, beta, NCAM, or ELAM-1. Both patient and HD BM stromal cell lines variably expressed ICAM-1, VCAM-1, and CD44. However, surface expression levels of these molecules did not correlate with the ability of the stromal cell lines to support DW34 cell growth. Taken together, these results suggested that BM microenvironment might play important roles in the pathogenesis of MM and RA.
We established a radiation-induced murine hematopoietic cell line, Y6, that could be induced to differentiate into macrophages by interleukin-6 (IL-6). IL-6 also induced growth inhibition and apoptosis in Y6 cells. Retinoic acid (RA) inhibited such effects of IL-6 on Y6 cells. The inhibitory effect of RA on the effects of IL-6 was not caused by the downregulation of the IL-6 receptor, because RA neither affected the expression of IL-6 receptor mRNA nor the expression of IL-6 receptor molecule on the cell surface. Furthermore, RA did not inhibit the IL-6-induced expression of junB mRNA, indicating that the expression of functionally active IL-6 receptor and the signal transduction pathway activating the junB gene are not inhibited by RA. IL-6-induced macrophage differentiation of Y6 cells was preceded by the downregulation of the c-myc gene, which was also prevented by RA. Because the inhibitory effect of RA on Y6 cells was reversible and seemed not to require de novo protein synthesis, the RA receptor by itself might be directly involved in the inhibition of the IL-6 signal transduction pathway. The results indicated that the IL-6 signal transduction pathways leading to the induction of macrophage differentiation and junB gene expression can be dissected by RA.
To clarify the components of cellular immunity responsible for defense against the clonal development of myeloma cells, we tested the capacity of human peripheral blood lymphocytes (PBLs) to inhibit the growth of 3 human myeloma cell lines (RPMI 8226, OPM-1, and OPM-2). RPMI 8226 was found to be sensitive to PBLs, showing almost complete growth arrest when cultured with PBLs for 72 h. Inhibition of the growth of RPMI 8226 cells required direct cell-to-cell contact but not presensitization of the PBLs to the target cells, and did not depend on the generation of soluble factors. CD3+, CD4-, CD8- and CD16- cells were found to be the major subset contributing to inhibition of the growth of RPMI 8226 cells, and this growth inhibition was cytostatic rather than cytotoxic. These characteristics distinguished it from growth inhibition mediated by the natural killer system. Impaired PBL-mediated growth inhibition of RPMI 8226 cells was found in patients with various hematologic diseases, including myeloma. It therefore appears that the CD3+, CD4-, CD8- and CD16- cell subset might be involved in tumor immunity in myeloma.
A new B-cell line (ONHL-1) was established from non-Hodgkin's lymphoma. ONHL-1 was free from Epstein-Barr virus nuclear antigen and expressed CD20, CD24, and slg (mu, delta, gamma and kappa), thus being equivalent to the mature B-cell stage. Chromosome analysis revealed a markedly abnormal pattern including 14q+ and 6q-. In accordance with the positive expression of surface kappa light chains, one of the kappa genes was found to be rearranged. However, rearrangement of the lambda locus was also detected, contrary to the supposed hierarchy for the rearrangement of the light-chain genes. Further, the rearranged fragments of the JH, C lambda, and bcl-2 genes were of the same size in the EcoRI and HindIII digests on the same filter. This may suggest that the bcl-2 gene is juxtaposed with the JH and C lambda locus. The proliferation of ONHL-I was inhibited by adding Staphylococcus aureus Cowan 1 or 12-O-tetradecanoyl-phorbol-13-acetate. During this growth inhibition, the expression of c-myc decreased, while that of bcl-2 mRNA remained steady. This result suggests that not the bcl-2 gene but other oncogenes, such as c-myc, play a key role in the proliferation of ONHL-1. This agrees with the hypothesis that the bcl-2 gene is not concerned with aggressive proliferation but with cell survival. This new cell line will therefore be of value in studying the differentiation and tumorigenesis of B cells.